1. Field of the Invention
This invention relates to a starter motor assembly for starting an engine and, more particularly, to a starter motor assembly that has a return spring spaced from a pinion assembly of the starter motor assembly. This application is being filed concurrently with U.S. patent application Ser. No. 10/022,166, entitled Engagement and Disengagement Mechanism for a Coaxial Starter Motor Assembly, with inventors David A. Fulton and James D. Stuber, and assigned to Delco Remy America, Inc.
2. Background of the Invention
Starter motor assemblies to assist in starting engines, such as engines in vehicles, are well known. The conventional starter motor assembly broadly includes an electrical motor and a drive mechanism, which generally includes a mechanism for engaging and disengaging a pinion-type gear with an engine flywheel. The electrical motor is energized by a battery upon the closing of an ignition switch. The drive mechanism transmits the torque of the electrical motor through various components to the engine flywheel, thereby cranking the engine until the engine starts.
In greater detail, the closing of the ignition switch (typically by turning a key) energizes a solenoid with low current. Energization of the solenoid moves a metal solenoid shaft or plunger in an axial direction. The movement of the solenoid plunger closes electrical contacts, thereby applying full power to the electrical motor. The movement of the solenoid plunger also biases a pinion-type gear into engagement with a ring gear of the engine flywheel. Once the vehicle engine is started, the operator of the vehicle will open the ignition switch. The solenoid is thus turned off (i.e., deenergized), but the electrical contacts are still closed. To prevent run-on of the electrical motor, and subsequent damage, the engagement and disengagement mechanism must be designed to break the electrical contacts and disengage the pinion-type gear from the engine flywheel.
Starter motors assemblies can be either xe2x80x9cbiaxialxe2x80x9d or xe2x80x9ccoaxial.xe2x80x9d These terms relate to the location of the solenoid and solenoid plunger with respect to the armature shaft of the electrical motor. In a biaxial starter motor, the solenoid and the solenoid plunger are attached to the motor casing, with the solenoid plunger spaced away from and generally parallel to the armature shaft. In a coaxial starter motor, the solenoid is typically placed in the motor casing so that the solenoid plunger is aligned in the same axis with the armature shaft. The coaxial assembly is considered to be more compact and universally adaptable than the biaxial assembly. The present invention is directed to a coaxial assembly.
Once the electrical contacts are closed and full power is applied from the battery to the electrical motor, the motor""s armature shaft subsequently rotates at a high speed. A planetary gear assembly, coupled to the armature shaft, reduces the speed of rotation of the armature shaft. The planetary gear assembly includes a drive shaft that rotates at that reduced speed. The end of the drive shaft opposite the planetary gear assembly is coupled with a pinion, preferably by a pinion shaft. Thus, the pinion rotates due to the rotation of the planetary gear drive shaft, which in turn rotates (again, at a reduced speed) due to the rotation of the electrical motor armature shaft.
Starter motor assemblies typically include a one-way clutch that is utilized to allow the planetary gear drive shaft to rotate at higher speeds and/or in the opposite direction from the cranking of the engine and to ensure that these higher rotational speeds or opposite directional velocities are not transmitted to the electrical motor armature shaft. In coaxial starter motor assemblies, the clutch is sometimes built around a ring gear positioned between the planetary gear drive shaft and the electrical motor armature shaft.
As stated above, energization of the solenoid also moves the solenoid plunger in the axial direction to move the pinion into engagement with the engine flywheel. In coaxial starter motor assemblies, typically the plunger is coupled to the pinion such that the movement of the plunger in turn moves the pinion in that same axial direction.
The pinion includes a plurality of gear teeth on its external surface for engagement with the engine flywheel. Thus, when the pinion is biased toward engagement of the flywheel and is rotating, the engagement of the pinion with the ring gear of the flywheel in turn causes the flywheel to rotate, thereby cranking the vehicle engine.
For the energization of the solenoid assembly to move the solenoid plunger and hold the plunger for pinion-flywheel engagement, solenoid assemblies typically utilize two coils, a pull-in coil and a hold-in coil. In particular, both coils energize the plunger of the solenoid assembly to bias the plunger in the axial direction for engagement with the engine flywheel. The hold-in coil then holds the plunger in place to hold the pinion in the engagement position with the ring gear of the engine flywheel.
After the operator of the vehicle opens the ignition switch, which deenergizes the solenoid assembly, the magnetic field that caused the solenoid plunger to move decreases and at some point is overcome by a return spring. In particular, the return spring continually pushes against the pinion away from engagement with the engine flywheel. However, it is only at those times when the force of the return spring is greater than the magnetic field generated by the solenoid biasing the plunger toward the flywheel, as well as an axial thrust force, that the pinion is moved away from engagement from the flywheel.
Conventional return springs often contact the pinion or some part rigidly connected with the pinion, such as the pinion shaft or the drive shaft, in order to exert a force on the pinion to bias the pinion away from the engine flywheel. For example, U.S. Pat. No. 6,109,122, issued to Bori et al. (xe2x80x9cthe Bori et al. patentxe2x80x9d), and assigned to Delco Remy International, discloses a pinion shaft that includes a pinion spring surrounding it, with a pinion engaging one end of the pinion shaft. U.S. Pat. No. 4,924,717, issued to Aimo, discloses a spring fitted around an appendage of the pinion. U.S. Pat. No. 4,838,100, issued to Tanaka, discloses a spring that surrounds the pinion shaft between a bearing, which is rigidly fitted on the inner wall of tubular inner contact member in which the pinion shaft is disposed, and a retaining ring, which is secured to the periphery of the rear end portion of the pinion shaft. Similarly, U.S. Pat. No. 4,852,417, issued to Tanaka, discloses that the pinion shaft is returned by the action of a spring that is provided around the rear end of the pinion shaft.
Thus, the return springs discussed above will be in constant contact with the pinion or the pinion shaft and, thus, will be pushing against a part that is rotating. In some instances, the contact between the return spring and the pinion or the pinion shaft causes the return spring to rotate with the pinion or the pinion shaft as well.
Starter motor assemblies having return springs that contact the pinion or the pinion shaft suffer from several disadvantages. In particular, one disadvantage is the wear on the return spring due to the constant contact and/or rotation with the pinion or the pinion shaft. In addition, the rotation of the return spring may occur at high speeds, which can result in breakage of the spring.
The present invention is directed to a starter motor assembly having a housing. An electrical motor is provided in the housing having a rotatable armature shaft. A rotatable drive shaft is provided that is engageably linked with the armature shaft. A pinion assembly is provided in the housing that is engageable at one end with the drive shaft. The pinion assembly includes a pinion at the other end engageable with a flywheel of an engine. A solenoid assembly is provided in the housing for selectively energizing the electrical motor, wherein the solenoid assembly is coaxial with the drive shaft. The solenoid assembly includes a plunger having a bore. The plunger is engageable with the pinion assembly to move the pinion assembly including the pinion into engagement with the flywheel. A return spring is provided that is positioned at least in part within the bore of the plunger of the solenoid assembly for moving the pinion assembly including the pinion away from engagement with the flywheel. The return spring is spaced from the pinion assembly. Energization of the solenoid assembly moves the plunger to move the pinion assembly to engage the pinion with the flywheel. Upon deenergization of the solenoid assembly, the return spring moves the pinion assembly which moves the pinion from engagement with the flywheel.
In one embodiment, the starter motor assembly includes a contact member that engages the plunger and the pinion assembly so that movement of the plunger moves the pinion assembly. The contact member is positioned within the bore of the plunger and contacts a contact surface of the plunger. The contact member is further positioned within a groove formed around an external surface of the pinion assembly. A first end of the return spring pushes against the contact member. Upon deenergization of the solenoid assembly, the return spring moves against the contact member which in turn moves the pinion assembly to move the pinion from engagement with the flywheel.
In one embodiment, the contact member is penannular in shape. In another embodiment, the contact member is annular in shape. The contact member is preferably made of a case hardened steel, stainless steel, or brass.
In one embodiment, the starter motor assembly further comprises a plunger stop assembly provided around the pinion assembly. The plunger stop assembly includes a groove formed in a surface opposite a surface facing the flywheel. A second end of the return spring, which is opposite the first end of the return spring, pushes against the groove formed in the plunger stop assembly.
In one embodiment, the rotatable drive shaft is part of a planetary gear assembly provided in the housing. The planetary gear assembly includes a plurality of planetary gears engaged with the armature shaft. Each planetary gear is rotatable on a respective pin, and the pins are linked to the rotatable drive shaft.
In one embodiment, the starter motor assembly further includes a clutch assembly provided in the housing engageable with the drive shaft of the planetary gear assembly and the armature shaft. The clutch assembly has an inner clutch piece, an integrated clutch shell including an outer clutch piece, and rotation control means provided between the outer clutch piece and the inner clutch piece for preventing rotation of the inner clutch piece in a first direction and allowing rotation of the inner clutch piece in a second direction.
The present invention is also directed to a starter motor assembly including a housing. An electrical motor is provided in the housing that has a rotatable armature shaft. A rotatable drive shaft is provided that is engageably linked to the armature shaft. A pinion assembly is provided in the housing. The pinion assembly includes a pinion shaft that is engageable at one end with the drive shaft and includes a pinion at the other end engageable with a flywheel of an engine. The pinion shaft further includes a groove formed around an external surface of the pinion shaft. A solenoid assembly is provided in the housing for selectively energizing the electrical motor, wherein the solenoid assembly is coaxial with the drive shaft. The solenoid assembly includes a plunger having a bore. The plunger is engageable with the pinion assembly to move the pinion into engagement with the flywheel. A return spring is provided that is positioned around the pinion shaft without contacting the pinion shaft. The return spring is positioned at least in part within the bore of the plunger of the solenoid assembly. A contact member is provided that is positioned within the groove formed around the external surface of the pinion shaft. The contact member is also positioned within the bore of the plunger of the solenoid assembly. Energization of the solenoid assembly moves the plunger which in turn moves the contact member which in turn moves the pinion assembly to thereby engage the pinion with the flywheel. Upon deenergization of the solenoid assembly, the return spring moves the contact member which in turn moves the pinion assembly to move the pinion from engagement with the flywheel.
The present invention is also directed to a starter motor assembly including a housing. An electrical motor is provided in the housing that has a rotatable armature shaft. A planetary gear assembly is also provided in the housing. The planetary gear assembly includes a rotatable drive shaft that is engageably linked to the armature shaft. The planetary gear assembly also includes a plurality of planetary gears engaged with the armature shaft, wherein each planetary gear is rotatable on a respective pin and the pins are linked to the rotatable drive shaft. A pinion assembly is provided in the housing. The pinion assembly includes a pinion shaft that is engageable at one end with the drive shaft and includes a pinion at the other end engageable with a flywheel of an engine. The pinion shaft further includes a groove formed around an external surface of the pinion shaft. A solenoid assembly is provided in the housing for selectively energizing the electrical motor, wherein the solenoid assembly is coaxial with the drive shaft. The solenoid assembly includes a plunger having a bore. The plunger is engageable with the pinion assembly to move the pinion into engagement with the flywheel. A return spring is provided that is positioned around the pinion shaft without contacting the pinion shaft. The return spring is positioned at least in part within the bore of the plunger of the solenoid assembly. A contact member is provided that is positioned within the groove formed around the external surface of the pinion shaft. The contact member is also positioned within the bore of the plunger of the solenoid assembly. A plunger stop assembly is provided around the pinion assembly. The plunger stop assembly includes a groove formed in a surface opposite the surface facing the flywheel. One end of the return spring pushes against the groove of the plunger stop assembly. Energization of the solenoid assembly moves the plunger which in turn moves the contact member which in turn moves the pinion assembly to thereby engage the pinion with the flywheel. Upon deenergization of the solenoid assembly, the return spring moves the contact member which in turn moves the pinion assembly to move the pinion from engagement with the flywheel.
The advantages of the invention will be set forth in the description below, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by the combinations set forth in the attached claims.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.